The present invention relates to a stabilizing and control device for two bladed helicopter rotors. This device provides for exceptionally good stability of the helicopter.
The prior art already discloses stabilizing and control means for two bladed helicopter rotors comprising a tiltable bar, the central tilt axis of which intersects the axis of the rotor and is disposed parallel to the blade axes and wherein the bar comprises on each side of the rotor axis a mixing lever bar for adjusting the rotor blades via a swash or wobble plate. For example, relatively extensive stabilization is provided by the so-called Young stabilizer of U.S. Pat. No. 2,646,848 to A. M. Young. A continuous blade is employed which is hung on gimbals and which is capable of rotating about its lateral axis in addition to its stroke axis. The plane of rotation of the stabilizing bars according to Young remains in space on account of the gyrostatic action. As a result, the rotor blades are controlled in such a way that a restoring moment is engaged. Extremely good stability is obtained with this position switching system but the helicopter is now very difficult to control. It reacts very sluggishly to the control movement. This disadvantage can be partly eliminated by connecting between the stabilizing bar and the rotor axis dampers which carry the stabilizing bars to a specific extent during tilting of the rotor axis. As a result, the extent of position switching is reduced and a rotation speed modulation is introduced because when the rotor axis is subject to pitching or rolling motions the rotor resultant lags behind the rotor axis. However, this stabilizing action prevents sufficiently simple and effective control. It is difficult to accurately adjust the dampers. Soft dampers provide good stability but reduced controllability. Excessively hard dampers provide poor stability but good control.
U.S. Pat. No. 2,818,123 to S. Hiller, Jr. is also representative of the current state of the art in stabilization of two-bladed teetering rotors by means of mechanical gyro control devices, but this is basically a servo control system.